Process for producing synthetic lumber that is not attacked by insects



Patented Dec. 5, 1933 PROCESS FOR PRODUCING SYNTHETIC LUMBER THAT IS INSECTS NOT ATTACKED BY Orland R. Sweeney, Ames, Iowa, assignor to Iowa State College of Agriculture and Mechanical Arts, Ames, Iowa, a corporation of Iowa No Drawing. Original application June 27, 1929 Serial No. 374,274, now Patent No. 1,803,737

granted May 5, 1931. cation April 13, 1931.

8 Claim.

This invention relates to the process or method of treating synthetic lumber, paper or the like against attacks from insects. For purposes of illustration I will specifically consider andherein discuss the treating of synthetic lumber made from cornstalks against such attacks by ants and the like. To this end the invention may consist of, first; cooking the unshredded corn plant under pressure, second; allowing it to stand for a certain length of time without wash ing it, third; passing it through a rod mill or like, fourth; suitably washing the same, fifth; passing the washed product through a refining machine, sixth; treating said material with a suitable amount of water, seventh; adding to said mass a sizing material such as rosin or alum;,eighth; forming it into a board, ninth; drying it on a suitable machine, and tenth;

' spraying the formed board with corrosive sublimate. When such a board is formed it will be economical in manufacture, durable and strong in use, and will be free from the possibility of its deterioration by insects either boring or nesting inside the board or eating it. The step by step procedure may be varied as will hereinafter be explained.

Heretofore, a great deal of experimenting has been done in attempting to make suitable synthetic lumber from cornstalks and from this,

standpoint I might state that my United States Letters Patent on a process relating to the production of synthetic lumber from cornstalks, Patent No. 1,803,737, under date of May 5, 1931, and of which this invention is a division, goes into great detail to explain.

Sufllce it to say that the examination of the cornstalk shows that it is composed of a hard outer shell called the cortex. This cortex surrounds a soft pulpy material known as pith or parenchyma, and this pith surrounds elongated cell fibers called vascular bundles. Any processing of this material is difiicult because of the different physical properties. For example, if the grinding machinery is not especially adapted to the purpose, the pith will be beat to a jelly long before pieces of the outside fibers are reduced to a suitable pulp.

This causes the mat forming machine to become clogged and produce an unsatisfactory product. Likewise in the digesting of the corn- Divided and this appli- Serial No. 529,883

stalks with chemicals, no wholly satisfactory process has been worked out because the pith and vascular bundles are completely hydrolyzed and disintegrated before the cortex is properly cooked.

In the standard practice it is the custom to shred or otherwise comminute the cornstalks before subjecting them to cooking or chemical treatment.

I have found that if the constalks be unshredded and then fed into the digester as they come in bales or directly from the field, before they have been give any serious mutilation, and that if the diges ion be carried out using approximately pure water, or in other words water whose pH value does not vary greatly from 7.0, and that if these wholeunmutilated stalks are subjected to ,a pressure of from thirty to one hundred pounds in contact with hot water, that there results a product which when properly macerated gives a board of great strength and of highly desirable properties for use in the arts.

I have also found that it is advisable after cooking the cornstalks for from one to three hours under such a pressure with hot water, that the fibers will be made tougher and that the pith cells will draw into fiber better and be removed more completely from the fibrous cortex cells if I allow the cooked stalks to stand for from four to twenty-four hours before they are further handled in the processes. This standing has a double advantage in that it allows the fibers to absorb from the cook liquors ligneous or pentosic materials which probably partly oxidize and at the same time the greater amount of the cooking liquors drain away thus reducing the necessity for excessive washing of the material.

In order to get the best results from the water digested fibers or cornstalks as prepared in the foregoing manner, I next pass the cornstalks through a heavy rod mill. This rod mill is of the usual construction consisting of a large drum mounted for rotation and having a plurality of heavy rods therein.

As the drum revolves on its axis the rods naturally either tumble over each other or rise upon the side of the drum and slide down continuously. It is obvious that if the rods tumble from the top portion of the drum downwardly,

a pounding action will result, whereas if the rods slid down the side they will give a rubbing action to the material inside the drum.

For my purposes I prefer the rubbing action as it draws the pith cells into long fibers which do not jell up and which work better when commingled with the tough, strong cortex The obtaining of this result will vary with the difierent types of rod mills, but any skilled workman can easily determine the speed. the drum should rotate for realizing this rubbing action. Results will also depend on the rate the cornstalks are fed into the mill. Obviously the larger the rods and rod mill the greater the feed must be in order to produce satisfactory fiber. I have found that it is best to run the cornstalks through at such a rate as to cause the cortex fibers at the discharge end to vary in lengths from very short fibers to fibers 'of about one-half inch in length. Best results are not generally obtained by attempting to completely reduce the pulp in the rod mill. By passing the cornstalks through at a rate to give fibers or the above-mentioned dimensions, the pith is not excessively jelled, but is drawn into fibers. There will also be produced a small percentage of thread-like fibers several inches in length which is very desirable.

It is necessary to feed into the rod mill at the same time that the stalks are going through, an amount or" water such as to make the corn stalk fiber come from the discharge freely. The amount or this water will be at least five hundred per cent or the weight of the cornstalks fed into the mill.

After the pulp has come through the mill it is now coarse enough to be free on a screen which is so positioned as to receive the pulp. It is upon this screen that the cornstalk pulp is washed with water to remove a certain amount of the pentosans and lignins produced during the water cooking. This washing must not be too thorough because the adhesive properties of these before-mentioned materials are desirable. If, however, none of the lignins or pentosans are washed out, the board will not be free enough on the machines used to make up the same. The screen should be of approximately forty mesh and may be either of the inclined sheet type or the rotating cylinder type. As the pulp travels down and across the screen it is washed by the Water sprayed on it which can be controlled by a valve in the water line.

If a very refinedboard is desired, the pulp from the washing screen should be passed through a refiner in order to take out the small pieces of material which are sometimes termed shiners or chives. After the pulp is washed, a suitable amount of water is added to the same and to this mass usually is added a sizing material such as rosin or alum. The mass is then conveyed to the board forming machine as is well known in the art.

The above discussion will give a general idea of one way of making and forming a synthetic lumber and will form a basis upon which I may discuss the treating of the same against insects. Therefore, generally I would state that this invention consists of spraying a substance onto the board that is very poisonous to the insects. I

When the pulp is placed on the board forming machine it is pressed in the usual manner by mea er rollers or the like and. the water removed from the same. The water thus removed is generally called white waters and I have found that for economy or water consumption it is desirable to use this water by returning it to the process. I use it direct for washing the pulp and for diluting the pulp in the refining machine.

After the board mat is formed it is then pressed and dried in the usual manner by suitable pressing and drying machinery which delivers the formed board. in a hot' condition. is at this point that I spray a solution of corrosive sublimate, which is an excellent poison for successfully combating insects onto the heated boards, which due to the below normal dryness will readily absorb the solution of cor rosive sublimate, thereby making the board in sect-proof. The corrosive sublimate will more fully impregnate the .boards if they are stacked one on top oi the other and allowed to stand in such condition for a certain length of time.

Another method oi treating the board is to spray the corrosive sublimate on the board mass before it reaches the pressing and drying ma= chinery. However, in either case the board be successfully treated against insects.

The habit of many insec s such as termites or white ants is to bore into a board at the end and penetrate the interior of the board without afiecting the surface of the board, and after pieces with water, forming the mass into lumber by pressing and heat drying, and lastly spraying said lumber with a corrosive sublimate, while said lumber is still warm from said heat drying.

2. The process of manufacturing and produc ing a synthetic lumber from cornstalks consisting of the cooking of the cornstalks in water under pressure, discharging thematerial from the cooker, breaking the material into particles by a suitable machine, adding liquid to the particles, forming the mass into lumber by pressing and heat drying, and last spraying said lumber with a corrosive sublimat/e, while said lumber is still warm from said heat drying.

3. The process of manufacturing and producing synthetic items from cornstalks consisting in the cooking of the unshredded corn plant in water under pressure, discharging the material from the cooker, rubbing and breaking the corn stalks into elongated particles by a suitable machine, treating the particles with water, forming the mass into items by pressing and heat drying, and last spraying said items with a corrosive sublimate solution, while said lumber is still warm from said heat drying.

4. The process of rendering synthetic insulating lumber free from the attack of insects, consisting at the time of manufacturing the same of breaking up of the material to be used for the making of the insulating lumber into fine pieces, the commingling of the pieces with water, 359

cidewhflethesaidlumberisstillhottromtho heat drying.

8. The process 0! rendering synthetic insulating lumber made from cornstalks free from attacks by insects, consisting in the raising of the synthetic lumber to a high temperature, and while the said lumber is in such a highly heated state, the spraying of the same with a liquid insecticide.

ORLAND R. SWEENEY. 

